Feature Request: Amazon Q Personas for Role-Based AI Assistance

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue

### Operating system

macOS 15.5.0 (24F74)

### Expected behaviour

Users should be able to define and toggle between different personas (e.g., frontend, security, QA engineer) when interacting with Q. Each persona would pre-configure approach, knowledge focus, and response style for specific engineering disciplines. Implementation could include:

- Predefined personas for common roles (frontend, backend, security, QA, DevOps)
- User-customizable personas for team-specific needs
- Simple invocation methods like `q chat --persona security` or `@frontend` tags as you are writing a prompt I could say @frontend please focus on the following.
- Persona-specific knowledge prioritization (e.g., security persona emphasizes threat modeling, frontend persona focuses on performance and accessibility)

This would eliminate the need to repeatedly explain context and role in each interaction, streamlining workflows for developers who work across multiple domains or in teams with distinct responsibilities.

### Actual behaviour

-

### Steps to reproduce

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